Scuba cylinders are containers for compressed air. They are equipped at the top with a valve for regulating airflow and the choice of a valve will depend on its intended use. For example, when the use is recreational, a K-valve is usually employed; this is similar to an on-off valve in a water faucet.
On the other hand, when the airflow must be regulated to coincide with a specific tank pressure, a J-valve is used.
Still another valve, a DIN, is employed when high pressures are to be encountered.
Accordingly, it is essential for user safety that every scuba cylinder, and its associated parts, be carefully chosen and properly maintained.
Maintenance, however, is a serious problem and the injuries which can be attributed to scuba cylinder use, are due in large part to the manner in which diving tanks are made.
As a rule, scuba cylinders are made of aluminum and steel. A steel cylinder is stronger and it can hold more air per cubic foot than an aluminum cylinder; however, steel has serious disadvantages. For one, it is heavier. Also, steel rusts, and although the exterior can be galvanized to prevent corrosion, the interior cannot because the zinc used in the galvanizing process adversely affects air purity.
Also, it is not possible to obtain cylinders which are flat on the bottom. Present manufacturing methods produce only cylinders which are round at the base and, as a result, they cannot be made to stand upright unless they are fitted with a boot.
A `boot` is a cover made of rubber or plastic which is placed onto the bottom of a scuba cylinder. Some are made flat on their sides to prevent the tank from rolling when stacked.
Another difficulty with present-day scuba tanks is their cylindrical shape, a feature which makes it impossible to leave them unattended or put them in a stack. As a result, it is not uncommon to see scuba tanks roll and hit against one another.
Because of this `rolling` tendency, scuba cylinders are sometimes placed in a fabric or plastic sleeve so as to cushion the blow when one tank hits against another; however, the use of such sleeves has not prevented the tanks from becoming severely damaged.
Aluminum tanks provide improvement over steel because they are lighter. Also, they do not rust; instead, the aluminum oxidizes (i.e., anodizes) and forms a film which protects against corrosion.
These advantages, however, are more than offset by the fact that aluminum is a relatively soft metal whose malleable properties make it susceptible to denting and gouging.
Also, aluminum cylinders have an exterior surface which (like steel), is smooth and featureless. This makes them difficult to grasp and carry. Accordingly, when they are moved from one location to another, the tendency is to hoist and carry them by the valve stem and this, when repeatedly done, will ultimately cause damage to the valve assembly.
Accordingly, there is a need for a scuba cylinder which can be easily grasped, carried, and safely stored.
One solution to the hoisting and carrying problem is the Scuba Tank-Pack Rack produced by Pelican Products. This Rack holds up to six cylinders, U.S. or foreign made, with or without boots. It is on the order of an oversized wire dish drain and the wire is coated with plastic. Once the scuba tanks are in the rack, it is carried onto a boat where it can be deck-mounted. The difficulty with this rack is that it fails to provide a means for conveniently carrying individual cylinders; nor does it provide a means by which they can be stacked one atop the other.
Another known carrying system is the Scuba Caddy manufactured by Pier Industries, Inc. This is a base plate having a centrally disposed post equipped with neoprene bumpers. In this system, four scuba tanks are placed onto the base plate and held in an upright position against the bumpers by elastic cords.
Unfortunately, this system too does not solve the cylinder-carrying problem nor does it provide means by which scuba tanks can be assembled and safely stacked one atop the other.
Accordingly, there is a need for a scuba cylinder which can be easily lifted and conveniently carried from one location to another without the need for a rack, caddy or other adjunct.
Also, there is a need for a scuba cylinder which can be conveniently stacked and stored with other like-configured cylinders one atop the other.